An undisturbed one.... The two examples I was thinking of were on a disturbed landscape, but from an agricultural side. From an agricultural side, a species like an ox-eye daisy, which is coast to coast, can overtake what is considered to be a healthy hayfield or a healthy grazing field and it can overtake that range land and it's no longer palatable to cattle. Another one is orange hawkweed, or the hawkweed family. Those are very aggressive and they don't need to have disturbed lands.
On December 1st, 2011. See this statement in context.